Studies on a high molecular weight, salt-soluble chromatin isolated from rabbit thymus nuclei will be continued. The location of histone H1 is of major interest. It's susceptibility to removal by high salt and to protease action will be examined in an effort to find its relationship to nucleosomal core and to the internucleosomal DNA. The nucleosome sub-unit is also being studied. Methods have been developed to isolate complexes containing 200 base pairs of DNA as well as 140 base pairs of DNA. Using Mg ion precipiation and circular dichroic spectrophotometry, the conformation of DNA will be examined and perturbations due to change in the ionic environment investigated.